The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
The World Wide Web (“Www”) is a global information space. Text documents, images, multimedia and many other items of information, referred to as resources, are identified by short, unique, global identifiers called Uniform Resource Identifiers (“URIs”) so that each can be found, accessed and cross-referenced in the simplest possible way.
The World Wide Web Consortium (“W3C”) is an international consortium that develops standards for the World Wide Web. The W3C defines a “Web service” as a software system that is designed to support interoperable machine-to-machine interaction over a network. This definition encompasses many different systems, but in common usage, “Web service” refers to those services that use SOAP-formatted Extensible Markup Language (“XML”) envelopes and that have their interfaces described using Web Services Description Language (“WSDL”). Web services allow devices and applications to communicate with each other over one or more networks without the intervention of any human being, while using the same suite of protocols (e.g., Hypertext Transfer Protocol (“HTTP”)) that a human being would use to communicate with such devices and applications over one or more networks.
The specifications that define Web services are intentionally modular, and, as a result, there is no one document that defines all Web services. Instead, there are a few core specifications that are supplemented by other specifications as the circumstances and choice of technology dictate. Common core specifications are SOAP, WSDL, WS-Security, and WS-ReliableExchange. Different specifications address different tasks and functions.
SOAP is an XML-based, extensible message envelope format, with bindings to underlying protocols (e.g., HTTP and Simple Mail Transfer Protocol (“SMTP”)). Using XML, SOAP defines how messages should be formatted, so that those messages are formatted in such a way that the recipients of those messages (devices and applications) can understand those messages. SOAP can be used to perform remote procedure calls, for example.
WSDL is an XML format that allows Web service interfaces to be described along with the details of those interfaces' bindings to specific protocols. WSDL is typically used to generate server and client code, and for configuration.
The Devices Profile for Web Services (DPWS) defines a minimal set of implementation constraints to enable secure Web service messaging, discovery, description, and eventing on devices. The DPWS specification defines an architecture in which devices run two types of services: hosting services and hosted services. Hosting services are directly associated to a device and play an important part in the device discovery process. Hosted services are mostly functional and depend on their hosting device for discovery. DPWS builds on the following core Web services standards: WSDL 1.1, XML Schema, SOAP 1.2, WS-Addressing, and further comprises WS-MetadataExchange, WS-Transfer, WS-Policy, WS-Security, WS-Discovery and WS-Eventing. The latest DPWS specification (published in February, 2006) is incorporated herein by reference as if fully disclosed herein.